drm/amd/display: Don't allow FPO if no planes

In DCN32/321 FPO uses per-pipe P-State force. If there is no plane, then
then HUBP is power gated, in which case any programming in HUBP has no
effect and the pipe is always asserting P-State allow. This is contrary
to what we want to happen for FPO (FW should moderate the P-State
assertion), so block FPO if there's no plane for the FPO pipe.
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Reviewed-by: Samson Tam <samson.tam@amd.com>
Reviewed-by: Chaitanya Dhere <chaitanya.dhere@amd.com>
Signed-off-by: Alvin Lee <alvin.lee2@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource_helpers.c

@@ -524,13 +524,14 @@ static int get_refresh_rate(struct dc_stream_state *fpo_candidate_stream)
  *
  * Return: Pointer to FPO stream candidate if config can support FPO, otherwise NULL
  */
-struct dc_stream_state *dcn32_can_support_mclk_switch_using_fw_based_vblank_stretch(struct dc *dc, const struct dc_state *context)
+struct dc_stream_state *dcn32_can_support_mclk_switch_using_fw_based_vblank_stretch(struct dc *dc, struct dc_state *context)
 {
 	int refresh_rate = 0;
 	const int minimum_refreshrate_supported = 120;
 	struct dc_stream_state *fpo_candidate_stream = NULL;
 	bool is_fpo_vactive = false;
 	uint32_t fpo_vactive_margin_us = 0;
+	struct dc_stream_status *fpo_stream_status = NULL;
 
 	if (context == NULL)
 		return NULL;
@@ -559,10 +560,21 @@ struct dc_stream_state *dcn32_can_support_mclk_switch_using_fw_based_vblank_stre
 		DC_FP_END();
 		if (!is_fpo_vactive || dc->debug.disable_fpo_vactive)
 			return NULL;
-	} else
+	} else {
 		fpo_candidate_stream = context->streams[0];
+		if (fpo_candidate_stream)
+			fpo_stream_status = dc_state_get_stream_status(context, fpo_candidate_stream);
+	}
 
-	if (!fpo_candidate_stream)
+	/* In DCN32/321, FPO uses per-pipe P-State force.
+	 * If there's no planes, HUBP is power gated and
+	 * therefore programming UCLK_PSTATE_FORCE does
+	 * nothing (P-State will always be asserted naturally
+	 * on a pipe that has HUBP power gated. Therefore we
+	 * only want to enable FPO if the FPO pipe has both
+	 * a stream and a plane.
+	 */
+	if (!fpo_candidate_stream || !fpo_stream_status || fpo_stream_status->plane_count == 0)
 		return NULL;
 
 	if (fpo_candidate_stream->sink->edid_caps.panel_patch.disable_fams)

drivers/gpu/drm/amd/display/dc/dml/dcn32/dcn32_fpu.c

@@ -3465,7 +3465,15 @@ void dcn32_assign_fpo_vactive_candidate(struct dc *dc, const struct dc_state *co
 	for (i = 0, pipe_idx = 0; i < dc->res_pool->pipe_count; i++) {
 		const struct pipe_ctx *pipe = &context->res_ctx.pipe_ctx[i];
 
-		if (!pipe->stream)
+		/* In DCN32/321, FPO uses per-pipe P-State force.
+		 * If there's no planes, HUBP is power gated and
+		 * therefore programming UCLK_PSTATE_FORCE does
+		 * nothing (P-State will always be asserted naturally
+		 * on a pipe that has HUBP power gated. Therefore we
+		 * only want to enable FPO if the FPO pipe has both
+		 * a stream and a plane.
+		 */
+		if (!pipe->stream || !pipe->plane_state)
 			continue;
 
 		if (vba->ActiveDRAMClockChangeLatencyMarginPerState[vba->VoltageLevel][vba->maxMpcComb][vba->pipe_plane[pipe_idx]] <= 0) {

drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.h

@@ -163,7 +163,7 @@ void dcn32_determine_det_override(struct dc *dc,
 void dcn32_set_det_allocations(struct dc *dc, struct dc_state *context,
 	display_e2e_pipe_params_st *pipes);
 
-struct dc_stream_state *dcn32_can_support_mclk_switch_using_fw_based_vblank_stretch(struct dc *dc, const struct dc_state *context);
+struct dc_stream_state *dcn32_can_support_mclk_switch_using_fw_based_vblank_stretch(struct dc *dc, struct dc_state *context);
 
 bool dcn32_allow_subvp_with_active_margin(struct pipe_ctx *pipe);